I have a grey square that has appeared on my screen which I have taken screen shot on the problem as my lecture has also tried to remove it which it wont remove

[jamesb98039240]

I have a grey squared that has appeared on my color scheme have tried to remove it with my lecture as it wont remove every time we hit any other color the grey square follows is there any way we could get rid of it as I have taken screen shot for reference

yours kindly

James Brown.

[alisterblack]

What product are you working with?